Regenerative steam power plant in which an extraction turbine supplies steam to desuperheaters which serve to heat feed water



June 30, 1953 2,643,519

CZ. POWELL REGENERATIVE STEAM POWER PLANT IN WHICH AN EXTRACTION TURBINE SUPPLIES STEAM TQ DESUPERHEATERS WHICH SERVE TO HEAT FEED WATER Filed March 2, 1949 u Bnventor b4: Richard. C. Powell.

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(Iltornegs iatented June 30, 1953 UNITED STATES PATENT OFFICE 4 REGENERATIVE STEAM POWER PLANT IN WHICH AN EXTRACTION TURBINE SUP- PLIES STEAM TO DESUPERHEATERS WHICH SERVE TO HEAT FEED WATER Richard C. Powell, Oakland, Calif.

Application March 2, 1949, Serial No. 79,259

Claims. 1

This invention relates to so-called regenerative cycles, used in turbine steam plants, and in which steam tapped from turbine stages is passed through feed water heaters.

As to those taps which sup-ply superheated steam it is known practice to carry out the heat exchange with the feed water in two phases, in the first of which the superheat is extracted from the steam, and in the second the heat is extracted from saturated (or substantially saturated) steam. As so carried out the feed water received heat alternately from a desuperheater and a saturated steam heater, and where there were several taps the heat exchange was not particularly good because the temperature differences were not highly favorable.

According to the present invention; when there are several taps which deliver superheated steam, the steam of 'all is desuperheated in a desuperheater or desuperheaters in which the heat exchange is with feed water which has already passed through the saturated steam heaters. Where several desuperheaters are used their water paths may be connected in parallel or in series, and where a series arrangement is used it is preferred that the last superheater in the series receives the hottest steam.

By the above procedures an improved heat recovery is aiforded without greatly complicating.

the circuit.

The precise nature of the exchangers is not material, and since the invention resides in the circuit the exchangers will be indicated diagrammatically according to an established Patent Office convention. Nothing is thereby implied as to the form of the heat exchangers, and the circuit can be laid out so simply as to be readily comprehended.

In the drawing:

Fig. 1 is a diagram of a circuit according to the invention, in which the water paths of the desuperheaters are in multiple.

Fig. 2 is a diagram of a circuit which is identical with Fig. 1 except that said water paths are in series.

Fig. 3 is a diagram of a system according to Fig. l elaborated by the use of secondary desuperheaters so that desuperheating occurs in more than one step. The first desuperheating step for all tap-s which supply superheated steam is effected in desuperheaters connected according to the invention.

Refer first to Fig. 1. The steam generator or boiler is indicated at 5 and supplies steam through line 6 to turbine l which drives electric generator 8, and exhausts from its last stage into 2 condenser 9. A feed pump ll draws condensate from the hot well of the condenser and returns it to the generator 5 through the regenerative system which involves the present invention. The parts 5 to II are understood to be conventional and are conventionally arranged.

Four taps Tl, T2, T3 and T4 withdraw steam from stages of turbine 'l. The first three are assumed to deliver superheated steam whereas T4 delivers steam which is saturated or substantially The Patent Ofiice convention for a heat exchanger is a shell with inlet and outlet connections, the shell enclosing a coil which also has inlet and outlet connections. On a purely arbitrary basis the desuperheaters and saturated steam heaters are here consistently drawn as if the feed water passed through the coil, simply as a means of facilitating tracing of the circuits.

Tap Tl leads to the shell of desuperheater DI and thence to the shell of saturated steam heater SI (the last in the series of such heaters). For the next tap the path is T2 to shell of D2 to shell of S2 and for the third tap the path is T3 to shell of D3 to shell of S3. T4 is connected directlyto the shell of S4.

The three coils WI, W2 and W3 of desuperheaters Dl, D2, D3 are connected in parallel between portions Fl and F2 of the boilerfeed line.

The feed pump ll delivers through the coils H4, H3, H2, HI of the saturated steam heaters S4, S3, S2, Sl the flow being in series and in the order just stated to feed line Fl.

The connections Cl, C2, C3, C4 return the drip to the condenser hot well.

Fig. 2 is absolutely the same as Fig. 1 except that coils W3, W2, Wl of the desuperheater are connected in series between Fl and F2.

In the embodiments of Figs. 1 and 2 the superheated steam supplied by taps Tl, T2 and T3 is desuperheated in Dl, D2 and D3 by heat exchange with feed water after the latter has passed through all the saturated steam heaters S4, S3, S2 and Sl.

In Fig. 2 in which the feed water connections are in series Tl which furnishes the hottest steam feeds Dl which is the last desuperheater in the water path, T2 feeds D2 which is next to last and so on. The same logic applies to the order of connections from the desuperheaters to the saturated steam heaters.

Thus the recovery of heat in the main desuperheating operations is effective to impart the highest practicable temperature to the feed Water, and a better total heat transfer results.

Sometimes it is impracticable to remove the entire superheat in one step. Where this is the case the arrangement shown in Fig. 3 may be adopted. Here the desuperheaters Which efiect the principal recovery of superheat are connected according to the invention. For illustrative purposes the multiple connection of Fig. 1 is chosen.

In Fig. 3 the parts identified by numbers to I I are the same as before and hence these numerals are used. Parts which correspond to lettered parts in Fig. 1 are identified by lower case letters.

As will be apparent the path ti, dI, sI is the same as in Fig. 1.

From t2 the path is to (12 thence to the shell of the secondary desuperheater E4 and thence to $2.

From 123 the path is to d3 thence to the shell of secondary desuperheater d5 thence to shell of tertiary desuperheater dB and thence to saturated steam heater s3.

The water path from pump I I is via M, h3, w6, 71,2, thence via 1114 and w5 in parallel, to h] and then by II through wI, wZ and 103 in parallel to T2 and generator 5.

Despite the fact that the secondary and tertiary desuperheaters d4, 115 and d6 are intercollated between saturated steam heaters in the water path, the invention is present because the main desuperheaters are connected according to the invention and afford its advantages.

In Fig. 3 a pump I2 is used to deliver drip to the feed water line as shown.

I claim:

1. In a regenerative steam power plant of the type in which superheated steam from a generator is expanded through an extraction turbine, means for heating the feed water, comprising in combination a plurality of desuperheaters, each having a water path and a steam path; a plurality of saturated steam heat exchangers, each having a steam path and a water path; a plurality of connecting means from respective extraction stages of said turbine afiording steam paths, each including the steam path of a desuperheater and the steam path of a heat exchanger connected in series; and means connecting the water paths of said desuperheaters and said heat exchangers in such order that the feed water passes through said desuperheaters after passing through said heat exchangers.

2. The combination defined in claim 1 in which the water paths of the desuperheaters are connected in parallel.

3. The combination defined in claim 1 in which the water paths of the desuperheaters are connected in series.

4. The combination defined in claim 1 in which the water paths of the desuperheaters are connected in series and the desuperheaters are arranged in the direction of feed water flow in the order of ascending steam temperatures.

5. The combination of a regenerative steam power plant of the type in which steam from a generator is expanded through a turbine and steam is tapped off from a plurality of turbine stages; saturated steam heaters each having a steam path and a water path; a steam flow connection between each of said saturated steam paths and a corresponding turbine tap; primary desuperheaters each having a steam path and a water path, the steam path of each of said primary desuperheaters being interposed in the steam flow connection between one of the taps and the corresponding saturated steam heater; at least one secondary desuperheater having a steam path and a water path, the steam path of said secondary desuperheater being interposed in the steam flow connection between one of said primary desuperheaters and the corresponding saturated steam heater; a feed water path including the water paths of the saturated steam heaters in serial arrangement, the water path of said secondary desuperheater being interposed in said feed water path between the water path of the corresponding saturated steam heater and the water path of another saturated steam heater in said series, the feed Water path passing ultimately through said primary desuperheaters; and connections for supplying condensate from the saturated steam heaters to the feed water path.

RICHARD C. POWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 938,309 De Ferranti Oct. 26, 1909 1,615,003 Bottomley et a1 Jan. 18, 1927 1,750,035 Brown Mar. 11, 1930 1,781,368 Davidson Nov. 11, 1930 1,846,047 Brown Feb. 23, 1932 FOREIGN PATENTS Number Country Date 206,651 Great Britain Nov. 15, 1923 255,050 Great Britain Oct. 28, 1926 284,204 Great Britain June 7, 1928 441,453 Germany Mar. 4, 1927 

